Xanthulules

I had a strange dream last night, a small part of which involved a heated argument about xanthulules. Xanthulules, if you didn't know (it was new to me, as well) are objects with all properties not had by chrysanthemums, and only those properties. I don't recall the precise point of contention about them, but Venn diagrams on the relations between the properties of xanthulules and the properties of chrysanthemums were involved.